Presentation on theme: "The end (of the beginning):. Questions to ask in deciding which test is appropriate: 1. How has each participant contributed to the data? (Individual."— Presentation transcript:
Questions to ask in deciding which test is appropriate: 1. How has each participant contributed to the data? (Individual score(s) or merely part of a frequency)? 2. If scores, then what kind of scores are they? (Interval, ratio or ordinal data?) 3. How many Independent and Dependent Variables? One IV and one DV? (t-test, Mann-Whitney, Wilcoxon, ANOVA, Friedman’s, Kruskal- Wallis). Two IV’s, with scores for each? (Correlation) One or two IV’s, and frequencies of occurrence? (Chi-Square) 4. Looking for similarities (relationships) or differences? (Correlations vs other tests) 5. Independent measures or repeated measures? (Does each participant do just one experimental condition, or do they perform more than one?) 6. Do the data meet the requirements for a parametric test? Interval or ratio data; normally distributed; similar variances.
Effects of food additives on children's activity levels: Group A: eat tartrazine-containing nosh. Group B: same nosh without tartrazine. DV: time spent running around. Effectiveness of different types of diet: Group A: MacDonalds-a-day. Group B: Atkins Diet. Group C: banana and lettuce leaf diet. Group D: eat a diet book every day. DV: weight loss after 1 month. Effect of lobotomy on ratings of Conservative Party: Group A: No lobotomy. Group B: Lobotomy. DV: ratings of attractiveness of Conservative Party "policy" on immigration.
Effects of food additives on children's activity levels: Group A: eat tartrazine-containing nosh. Group B: same nosh without tartrazine. DV: time spent running around. A: additiveB: no additive 115 156 114 156 147 185 6 mean:14.005.57 s.d.:2.680.98 Σ X1 = 84Σ X2 =39
Effects of food additives on children's activity levels: Group A: tartrazine: mean = 14.00. Group B: no tartrazine: mean = 5.57. top line of equation:
Effects of food additives on children's activity levels: Group A: tartrazine. Group B: no tartrazine. DV: time spent running around. bottom line of equation: Quicker ways of calculating these... =5.714= 36.00
Effects of food additives on children's activity levels: Group A: tartrazine. Group B: no tartrazine. Two-tailed test (just predicting "an effect" of additives): t = 7.79 with 11 d.f., p <.00005
Effects of age on levels of grumbliness: IV A: age. IV B: assessment of extent to which the world is going to the dogs. Effects of mobile phones on situational awareness: Each person does two conditions: they walk along Western Road either using a phone or not using a phone. DV: number of people bumped into. Effects of 4x4 ownership on driving ability: Group A: 4x4 owners. Group B: non-twatty-car owners. DV: average speed at which each driver passes cyclists and horse-riders.
Effectiveness of recycling campaigns: Three different campaigns, in different city districts: one pays people to recycle, one appeals to their conscience, and the third punishes them if they don't recycle. DV: measure weight of unrecycled materials in the rubbish of 20 residents in each district.
Effects of dermal fillers on attractiveness: Two groups of participants. One group rate a set of celebrities for attractiveness before the celebrities have lip plumping treatments; the other group rate them afterwards. Effects of lipsuction on body image satisfaction: Each of 15 patients rates their satisfaction with their body image on a 10-point scale. They do this twice, once before liposuction and once afterwards.
Zajonc's "Mere Exposure" effect for Simon Cowell: One group of people spend a day with him and then rate his attractiveness, the other group spend a day with someone else and then rate Simon's attractiveness. Does TV affect children's linguistic abilities? One group of four year-olds group watch "In the Night Garden", the other group watch "News at Ten". Two months later, we measure how many three-syllable words each of them can produce. Do I-Pods cause hearing loss? Hearing threshold (in decibels) measured in teenagers before buying an I-Pod and 6 months later. Is crime worse in city centres than in villages? The police leave an unlocked car in a dark alley in ten inner city areas, and in ten villages. In each case, they measure how long it takes before one of the locals steals the car's stereo.
Questions about the exam: When selecting an answer, can you change your mind after writing it in the answer box, or is it like those quiz shows where your first answer is your final answer? In Section 2 (pick a test and use it), do we have to show ALL workings out of the test we choose, or can we work it out in our own notebooks and just write the final answer on the exam paper? And if we do have to show all the workings, does it matter if some of the figures are wrong, but the final answer is correct? Is it possible to take two University-approved calculators into the exam or are you only allowed one? Who are the people who walk around in the exam room? What are they called? What do they do? Will you be there?
Questions about the exam: Suppose my value of t = -3.2, and the critical value of t in a table is 2.878. My obtained t is smaller than 2.878 (because -3.2 is smaller than zero), so does this mean it is not significant?? Answers are shown to two significant digits (e.g. 2.56, 31.95 etc.) Should we round numbers off during the calculations, or only round off our answer? When do you use a t-test, and when do you use a correlation? When do you use Chi-Square Test of Association, and when do you use the Goodness of Fit version? Which version of the standard deviation formula should I use (n, or n-1)? I think I'm pregnant - which test should I use?